Design of a Multi-Ion Detection System Based on IoT Technology and Its Application in Cement-Based Materials

Area of Science:

• Materials Science and Engineering
• Environmental Science
• Analytical Chemistry

Background:

• Cement-based materials undergo complex processes like leaching, corrosion, and hydration, driven by coupled ion migration and reactions.
• Existing methods for ion analysis often use discrete sampling or single-ion detection, limiting the ability to capture synchronized multi-ion dynamics.
• Understanding time-aligned multi-ion evolution is critical for interpreting these processes accurately.

Purpose of the Study:

• To develop and validate an Internet of Things (IoT)-based in situ system for simultaneous detection of multiple ions in cement-based materials.
• To enable real-time, synchronized monitoring of ion concentrations and pH.
• To provide a tool for better interpretation of coupled ion processes in cementitious systems.

Main Methods:

• Integration of ion-selective electrodes (for Cl-, Ca2+, F-, H+) with an analog-to-digital converter (ADS1115) and a microcontroller (ESP32).
• Development of a voltage amplification module for enhanced signal detection.
• System calibration and testing for sensitivity, repeatability, interference, and temperature effects.

Main Results:

• The developed system achieved high sensitivity (minimum resolvable concentrations of 10^-5 M for Cl-/F-, 10^-4 M for Ca2+) and a wide pH measurement range (2-12).
• Demonstrated excellent short-term repeatability (RSD < 0.12%) and characterized interferences (e.g., Br-/NO3- on Cl-) and temperature effects.
• Successfully applied to phosphogypsum-cement hardened pastes, capturing synchronized Ca2+ release, F- fluctuation, Cl- release, and pH evolution.

Conclusions:

• The IoT-based in situ multi-ion detection system provides synchronized, real-time data crucial for understanding complex ion interactions in cement-based materials.
• This technology overcomes limitations of conventional offline or single-ion methods, offering a more comprehensive approach to studying leaching and degradation.
• The system offers a valuable tool for research and quality control in cement-based solid waste management and construction materials.